Homochiral Metal-Organic Frameworks for Enantioselective Separations in Liquid Chromatography

Selective separation of enantiomers is a substantial challenge for the pharmaceutical industry. Chromatography on chiral stationary phases is the standard method, but at a very high cost for industrial-scale purification owing to the high cost of the chiral stationary phases. Typically, these materials are poorly robust, expensive to manufacture and often too specific for a single desired substrate, lacking desirable versatility across different chiral analytes. Here we disclose a porous, robust homochiral metal-organic framework (MOF), TAMOF-1, built from copper(II) and an affordable linker prepared from natural L-histidine. TAMOF-1 has shown to be able to separate a variety of model racemic mixtures, including drugs, in a wide range of solvents of different polarity, outperforming several commercial chiral columns for HPLC separations. Although not exploited in the present article, it is worthy to mention that the preparation of this new material is scalable to the multikilogram scale, opening unprecedented possibilities for low-energy chiral separation at the industrial scale

Evaluation of appendicitis risk prediction models in adults with suspected appendicitis

Background Appendicitis is the most common general surgical emergency worldwide, but its diagnosis remains challenging. The aim of this study was to determine whether existing risk prediction models can reliably identify patients presenting to hospital in the UK with acute right iliac fossa (RIF) pain who are at low risk of appendicitis. Methods A systematic search was completed to identify all existing appendicitis risk prediction models. Models were validated using UK data from an international prospective cohort study that captured consecutive patients aged 16–45 years presenting to hospital with acute RIF in March to June 2017. The main outcome was best achievable model specificity (proportion of patients who did not have appendicitis correctly classified as low risk) whilst maintaining a failure rate below 5 per cent (proportion of patients identified as low risk who actually had appendicitis). Results Some 5345 patients across 154 UK hospitals were identified, of which two‐thirds (3613 of 5345, 67·6 per cent) were women. Women were more than twice as likely to undergo surgery with removal of a histologically normal appendix (272 of 964, 28·2 per cent) than men (120 of 993, 12·1 per cent) (relative risk 2·33, 95 per cent c.i. 1·92 to 2·84; P < 0·001). Of 15 validated risk prediction models, the Adult Appendicitis Score performed best (cut‐off score 8 or less, specificity 63·1 per cent, failure rate 3·7 per cent). The Appendicitis Inflammatory Response Score performed best for men (cut‐off score 2 or less, specificity 24·7 per cent, failure rate 2·4 per cent). Conclusion Women in the UK had a disproportionate risk of admission without surgical intervention and had high rates of normal appendicectomy. Risk prediction models to support shared decision‐making by identifying adults in the UK at low risk of appendicitis were identified

Synthesis of Extra-Large Pore, Large Pore and Medium Pore Zeolites Using a Small Imidazolium Cation as the Organic Structure-Directing Agent

One common strategy in the search for new zeolites is the use of organic structure-directing agents (OSDA). Typically, one seeks to achieve a high specificity in the structure-directing effect of the OSDA. This study shows, however, that an OSDA lacking strong specificity towards any particular zeolite may provide opportunities for discovery when other synthesis parameters are systematically screened. Thus, 1-methyl-2-ethyl-3-n-propylimidazolium has allowed to crystallize the new large/medium pore zeolite HPM-16 as well as the recently reported extra-large pore -SYT and the medium/small pore and chiral STW. The sophisticated OSDA originally affording -SYT and the new simple OSDA have very little in common, both in terms of size, shape and flexibility, while both may still direct the synthesis of the same zeolite. In fact, molecular simulations show that the new OSDA is located in three different positions of the -SYT structure, including the discrete 8MR where the original organic could not fit.Peer reviewe

HPM-16, a Stable Interrupted Zeolite with a Multidimensional Mixed Medium–Large Pore System Containing Supercages

[EN] HPM-16 is a highly porous germanosilicate zeolite with an interrupted framework that contains a three-dimensional system of 12+10 10(12) 12+10-membered ring (MR) pores. The 10(12) MR pore in the b direction is a 10 MR pore with long 12 MR stretches forming 30 long tubular supercages. Along one direction the 10 MR pores are fused, meaning that the separation between adjacent pores consists of a single tetrahedron that is, additionally, connected to only three additional tetrahedra (a Q3). These fused pores are thus decorated by T-OH groups along the whole diffusion path, creating a hydrophilic region embedded in an otherwise essentially hydrophobic environment. The structure is built from highly porous 12 12 12 MR uninterrupted layers that are connected to each other through Q3 producing a second system of 10 10 10 MRpores. This zeolite can be extensively degermanated yielding a material with high thermal stability, despite its interrupted nature.The authors are grateful for financial support to the Spanish Ministry of Science Innovation and Universities (MICIU) (PID2019-105479RB-I00 project, AEI, Spain and FEDER, EU). SRGB also thanks MICIU for a Juan de la Cierva- Formación Research Contract (FJC2018-035697-I code reference). Synchrotron experiments were performed at beamline BL04 (MSPD) at the Spanish ALBA Synchrotron with the collaboration of ALBA staff, and special thanks are due to A. Manj n and A. Missiul. Centro T cnico Inform tico-CSIC, Trueno cluster facility of SGAI-CSIC is acknowledged for running the calculations. We also deeply thank C. Márquez- Álvarez for his kind help in characterization. The cRED data were collected at the Electron Microscopy Center (EMC), Department of Materials and Environmental Chemistry (MMK) in Stockholm University with the support of Knut and Alice Wallenberg (KAW) foundation-financed project 3DEM-NATUR.Peer reviewe

The Si-Ge substitutional series in the chiral STW Zeolite Structure Type

The whole compositional range (Gef = Ge/(Ge+Si)= 0 to 1) of zeolite STW has been synthesized and studied by a comprehensive combined experimental--theoretical approach. The yield of zeolite goes through a maximum and then drops at the GeO2 side of the series, following the inverse of the calculated free energy curve. The unit cell generally expands, roughly linearly, as the Gef increases, but a notable resilience to expansion is observed at the high silica side. This can be attributed to the more rigid character of SiO2 and the ability of Ge units to deform. Density functional theory calculations provide a new assignment of the previously controversial 19F MAS NMR resonances for occluded fluoride, which is based not only in the number of Ge atoms in the double-4-ring units but also on the way they are associated (namely, no Ge, isolated Ge, Ge pairs or closed Ge clusters). While we found an overall good agreement between the experimental and theoretical trends in preferential occupation by Ge of different crystallographic sites, the theoretical models show more sharp and abrupt tendencies, likely due both to limitations of the approach and to kinetic factors that allow metastable configurations to actually exist.The authors thank the Spanish Ministry of Science and Competitiveness for funding (Projects MAT2015-71117-R and CTP2016-80206-P). R. T. Rigo thanks CAPES (Brazil) for a PhD fellowship (process 99999.012012/2013-00). S. R. G. Balestra thanks the Spanish State Secretariat for Research, Development and Innovation for his Predoctoral fellowship (BES-2014-067825 from CTQ2013-48396-P).Peer reviewe